A four-compartment ABR with an effective volume of 28 L was used to investigate the application of an anaerobic baffled reactor (ABR) in treating sugar-producing wastewater. The results indicated that the reactor could start up at an influent OLR of 2.5 kgCOD/m 3 -d and temperature of 35degC. COD removal rate could reach 89% on the 5 th day. Then the influent COD increased from 5000 to 8000 mg/L, HRT decreased from 48 to 36 h, and OLR increased to 5.3 kgCOD/m 3 -d on the 9 th day. The reactor performed steadily from the 28 th day, with an average COD removal rate of 85.5%. The total volatile acids in the four compartments declined gradually, with acetic acid in the greatest proportion, followed by propionic acid and then valeric acid.